In such traveling shed weaving looms, the path of the shuttle is guided across the width of the fabric at least over a substantial portion of the longitudinal path portion by a guide reed. The shuttle is guided on a guide reed and moved, by magnetic coupling to magnetic shuttle moving elements, which are carried along the shed, for example by an endless chain, by being coupled together or the like.
U.S. Pat. No. 4,410,087, to which German Pat. No. 30 16 182 corresponds, describes a multi-system or multi-feed, back-to-back weaving loom, i.e. a loom with traveling shed built in back-to-back construction. On the front side and back side, respectively, the shuttles pass through a straight portion of their guide path and through the shed, so that, in the straight portion, one or more fabric webs can be made. The shuttles are driven by drive elements which are either coupled together or coupled to an endless chain. The drive elements carry permanent magnets on the side facing the shed and the shuttle likewise carries permanent magnets which are in magnetically coupled relation to the drive element magnets. The magnetic coupling provides for moving of the shuttles, as set forth in general principle in U.S. Pat. No. 3,618,640, Linka, to which German Pat. No. 1 785 147 corresponds.
The two essentially straight portions of the guide path of the shuttle are coupled by curved return portions in which the shuttle leaves the shed, and is guided in an essentially semi-circular return path. Two sprockets are located in the region of the return path over which either the drive chain or the connected drive elements and drive segments are carried which, upon passing through the return path, are spread out in fan shape. Before the shuttles can enter the shed in the portion next to the curved portion, that is, at the transition from the curve to the straight portion, it is necessary to guide the shuttle again on the guide reed. On the straight guide portions, the essentially straight guide reed guides the shuttles. A stable slide path is thus formed for the shuttles, which are magnetically coupled to the drive segments. The reed elements simultaneously form a guide for the weft beating-up lamellae.
The shuttles are coupled in the region of the semi-circular return paths by being directly coupled to the drive elements, so that, between the facing pole surfaces of permanent magnets of the drive segments and of the shuttles, the only interposed material is the plastic sliding foil formed on the shuttles. Such a plastic sliding foil is located on the shuttles on the pole surfaces facing the reed, in order to provide for low-friction sliding movement of the shuttles on the reed. The tiny air gap which results between the facing pole surfaces and the permanent magnets provides for substantial attractive forces. The basic problem arises, however, that the shuttle, after passing the semi-circular return path portion of the guide track, again must be placed on the respective straight-line portion of the guide path or guide track formed by the reed. The reed elements or lamellae have a finite width, based, for example, merely on mechanical strength considerations. Thus, as the shuttle runs on the reed, the air gap between the permanent magnets, the shuttle and the drive segments must be increased with respect to the gap formed only by the low-friction foil. Consequently, the shuttle must be moved counter the attractive force to increase the air gap. Of course, separation of the shuttle which would lead to separation from the drive elements due to an abrupt interposition of resistance against movement in the guide path of the shuttle must be absolutely avoided. Abrupt change in magnetic forces and movement of the shuttle also results in substantial noise and excessive wear and tear on the slide surfaces of the shuttles.
A typical speed of a shuttle is about 1.4 m/sec. If adjacent shuttles are spaced from each other by, for example, 20 cm, seven shuttles will engage the reed on a run-on portion thereof each second. The continuous engagement of the shuttles with the reed causes noise and subjects the slide surface to wear, both of which are objectionable and should be avoided.